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Electrical Arc Flash – Dangers and Protection


It is well known that one of the most important hazards, that is a main source of very serious electrical accidents, is related to the excistence of electric arc in the electromechanical equipment.

More specifically, the electric arc is possible when performing tasks that require stoping and starting the main voltage. It happens when two electrodes that are in contact with each other in such way that a low amperage electric current flows though, get a few millimeters apart. When that happens a spark is generated. That spark gets stabilized when the voltage remains at the appropriate level (40-45 Volts) and at the same time the gas that is situated between the electrodes acts like a bridge ensuring constant flow of electric current.

Depending on the intensity of the electric arc, the dangers that may appear are:

  • High temperature that can reach 1600°C, resulting to the melting of most of the materials in a typical installation.
  • Explosive forces – shock wave
  • Very loud noise
  • Very intense flash that include UV
  • Plasma release
  • Toxic smoke and fumes
  • Solid residue at very high speed

There are multiple consequences for an employee in such a situation. Burns, blindness, hearing loss, chest damage(from the electric shock) and extensive injuries that on their totality and severity can lead to death.

It is undeniable that it is extremely important to have all the collective and individual measures in place to effectively eliminate the dangers of the electric arc. To combat the effects it is very important to have the means for individual protection such as protective gear, gloves, head protection, mask and suitable footware that can offer the higher safety level for the employee when they are handling and maintaining electromechanical equipment.

In that regard it becomes clear that the sourcing of the protection gear must come with the required credentials e.g. certification according to european standards and requirements indicated by the CE marking and instructions for safe use from the manufacturer.

Specifically with the protective clothing against the electric arc, an important aid is the establishment of international and european standards according to IEC and EN respectively. These determine the set of specifications and restrictions.

The IEC 61482-1-2 standard and the respective european ΕΝ 61482-1-2, examine thoroughly the testing procedures the materials and final protective apparel must withstand.

It is worth noting that all the technical assessment studies coping with electrical accidents deal with the calculation and the specification of the incident energy of the electric arc (cal/cm^2) at different work positions in front of the electromechanical equipment in conjunction with the real operating conditions.

The most used tools for the incident energy calculation at these events are the IEEE 1684 and NFPA 70E standards.

Installation of electrical panels for the water pumping station of the Municipality of Dionysos


ARPEDON undertook the design, supply and installation of the new electrical panels for the water pumping station of the Municipality of Dionysos.

The pumping station houses 3 pumping units with different energy requirements.

The new electrical panel is a 4 field with 1 Inverter for pumping unit 140 kW and 2 Inverters for pumping units 75 kW.

Prior to the connection of the panels, the dielectric strength of the cables was checked and all the necessary checks were performed to ensure correct and safe execution.

The power outage of the pumping station was less than 3 hours in total.

For the delivery of the project, field tests were performed in all panels according to the standard EN 61439 by an accredited body (LABOR SA) where the results showed complete compliance.

Prevent leaks in air conditioning and cooling systems with permanent pressure sensors


air conditioning installation

Air conditioning and refrigeration systems suffer from leaks. Within a year it is not unlikely that 30% of the refrigerant gas in the circuit will be lost. As there is a legal requirement of permanent monitoring for certain categories of systems (Regulation (EU) No 517/2014), we considered it appropriate to do some testing to allow the filling of the system to be done on time and without any surprises.

Using an ON/OFF contact and a permanently installed pressure sensor on the suction side, we were able to reliably observe the behavior of the circuit during manual removal and addition of refrigerant gas.

Pressure sensor

This system, in normal operation with the compressor active, has a circuit pressure of 3.6 – 3.7 bar.

When the refrigerant gas is removed, the pressure drop is obvious.

After tests, we came up with two alarms for this installation on the Arpedon Mechbase platform.

A Minor alarm at the level of 3.3 bar that works as a warning and a Major alarm at 3 bar.

Both alarms automatically generate work commands in the maintenance software (CMMS) that is installed on that installation to control the measurements.

If your installation includes air conditioning/ or refrigeration units, we can help you diagnose leaks with the permanent Arpedon Maintnode. systems in a timely manner.

Any industrial sensor can be integrated into our products. The process of increasing capabilities is ongoing. Tell us about your applications

What is cavitation and how to prevent it


Have a pump that makes popping sounds, or sounds like it’s pumping marbles? If so, you may have a cavitation problem.

Pump cavitation can cause a number of issues for your pumping system, including excess noise and energy usage, not to mention serious damage to the pump itself. 

Cavitation image 1
Cavitation image 2
Cavitation image 3

Description of the phenomenon

Simply defined, cavitation is the formation of bubbles or cavities in liquid, developed in areas of relatively low pressure around an impeller. The imploding or collapsing of these bubbles in areas where fluid pressure increases, causes intense shockwaves inside the pump, causing significant damage to the impeller and/or the pump housing.

If left untreated, pump cavitation can cause:

  • Damage to the pump housing, impeller and/or shaft
  • Excessive vibration level – leads to premature sealing loss and bearing failure
  • Higher than necessary power consumption
  • Decreased flow and/or pressure

There are also two phenomena that exhibit similar behavior to cavitation and is necessary to be reported: re-circulation and aeriation or air entrapment.


Pump impeller

When a pump is in low pressure or high vacuum conditions, cavitation occurs. If the pump is “starved” or is not receiving enough flow, bubbles or cavities will form at the eye of the impeller. As the bubbles carry over to the discharge side of the pump, the fluid conditions change, compressing the bubble into liquid and causing it to implode against the face of the impeller.

An impeller that has fallen victim to suction cavitation will have large chunks or very small bits of material missing, causing it to look like a sponge. Damage to the impeller appears around the eye of the impeller.

Possible causes:

  • Clogging of the suction area
  • Pump is running too far right on the pump curve
  • Poor piping design
  • Poor suction conditions (NPSH requirements)


Recirculation image 1
Recirculation image 2

When a pump’s discharge pressure is extremely high or runs at less than 10% of its best efficiency point (BEP), re-circulation of fluid occurs. The high discharge pressure makes it difficult for the fluid to flow out of the pump, so it circulates inside the pump.  Liquid flows between the impeller and the housing at very high velocity, causing a vacuum at the housing wall and the formation of bubbles.

The implosion of those bubbles triggers intense shockwaves, causing premature wear of the impeller tips and pump housing. In extreme cases, discharge cavitation can cause the impeller shaft to break.

Possible causes:

  • Blockage in the pipe on discharge side
  • The pump operates too far left on the pump curve
  • Poor piping design



Air entrapment happens when bubbles are in the liquid before reaching the impeller.  This can happen when:

  • The liquid is aerated ( for whatever reason) near the pump inlet.
  • Liquid is near its boiling point, such as in a condensate pump.

While this problem is not always as damaging (or as loud) as the previous ones, it can certainly damage the impeller if left unchecked.

Preventive treatment actions

  1. Check filters and the check valves – clogs on the suction, or discharge side can cause an imbalance of pressure inside the pump.
  2. Reference the pump’s curve – Use a pressure gauge and/or a flowmeter to understand where your pump is operating on the curve. Make sure it is running at its best efficiency point. Running the pump off its best efficiency point not only causes excess recirculation, expect excessive heat, radial loads, vibration, high seal temperatures, and lowered efficiency.
  3. Re-evaluate pipe design – Ensure the path the liquid takes to get to and from your pump is ideal for the pump’s operating conditions. Designs with inverted “U”s on the suction side can trap air, while designs with a 90° immediately before the pump can cause turbulence inside the pump. Both result in suction problems and pump cavitation.

Cavitation is a common problem in pumping systems, but with proper pump sizing, pipe design, and care of the whole system, damage to pumps can be largely avoided.

A satisfactory method to determine which of these problems are taking place using ultrasound or vibration analysis is to slow throttle the discharge valve closed.

As the discharge valve is being throttled closed:

  • If noise and vibration get better – expect cavitation.
  • If noise and vibration get worse – expect re-circulation.
  • If noise and vibration stay the same – expect aeriation (or air entrapment).

5 Problems from Poor Lubrication

Assets with moving parts rely on the consistent application of lubricants to function properly. Facility managers who work to improve their condition monitoring strategies benefit from improved asset uptime and cost reductions. These two concepts go hand-in-hand. Lubrication is an essential facet of condition monitoring.

To ensure your program functions properly, avoid these five common lubrication mistakes:

1. Over-lubrication

You can have too much of a good thing. When an asset lacks grease, it will quickly make the problem known, usually by failing. At the other end of the spectrum, over greasing can have a similar effect. That’s why it’s important to remember that lubricants have volume of their own. Too much grease could actually cause an asset to jam, necessitating additional maintenance and hours of downtime.

Likewise, over-greasing may lead to seal failure. Grease guns can produce an extraordinary level of pressure, and, in excess, harm bearings. Similarly, when grease dries and cracks, the pressure of additional lubricant can cause it to break apart, further damaging the bearings. An ultrasound reading can help technicians know when enough is enough.

2. Under-lubrication

A lack of lubricant is likely one of the easiest problems to spot. Assets that aren’t properly maintained will make themselves known in short order. Typically, excess heat and sound will radiate from the asset until failure. Alone, these symptoms are easy to detect, but within a noisy facility, they could go unnoticed.

Ultrasound equipment such as the Ultraprobe® 201 Grease Caddy can help facilities save on operating costs by providing a visualization of ultrasonic waves. In doing so, personnel will know exactly when an asset needs lubricating and when it’s in working order. This process saves man-hours so they can be applied to situations of greater need. Plus, the device is easy to use, even in crowded and noisy environments.


3. Using the wrong lubricant

Not only can using the wrong lubricant lead to asset failure, but it may also void the machinery’s warranty. Machine manufacturers will typically recommend specific lubricants for each asset. These guidelines should be taken seriously, or else the money for a replacement will likely come from your department’s budget.

As reported in Machinery Lubrication magazine, viscosity is one of the most important properties of a lubricant. Using an oil or grease with a viscosity that varies from the manufacturer’s recommendation is a recipe for failure. Read all documentation carefully, and follow guidelines exactly.

It’s also important to note that additives will change the composition and viscosity of your lubricants. If adding foam agents, antioxidants or corrosion inhibitors to your lubricant, check to see that it hasn’t altered to solution beyond the figures set by the asset’s manufacturer.

4. Mixing lubricants

Not all lubricants are created equal. In fact, mixing the wrong kinds of lubricants together can be just as damaging as not lubricating at all. According to Machinery Lubrication magazine, mixing synthetic and mineral-based lubricants can cause major problems, leading to leakages and complete failures.

According to the source, when the wrong lubricants mix, they risk expanding or shrinking nearby seals, causing them to fail. Such problems result in increased spending, as those assets must be replaced.

Similar problems occur when an incompatible thickener is added to grease. The mixture can become unstable and inappropriate for use on most machinery. The consistency of the lubricant may vary greatly and become unreliably. Not only does the machinery suffer as a result, but the grease must be tossed out too, leading to further expenses.

5. Lubricant contamination

One of the chief causes of premature bearing failure is lubricant contamination. Not only does contaminated lubricant harm machinery, but it can also be expensive to remove and clean. Understanding how and why contamination occurs is the first step to preventing premature failures. For instance, contamination may come from particles in the ambient air, dirt from outside the facility or from agents within the machine itself.

A condition monitoring policy that includes housekeeping protocols will ensure that contamination has a minimal impact on asset uptime. However, visual inspection may not be sufficient to determine if contamination has occurred. An ultrasound tool can pinpoint discrepancies in the ultrasonic output of a bearing, notifying maintenance personnel in well in advance of equipment failure.

An improved lubrication program starts with accurate data. Whether your facility utilizes a condition-based lubrication strategy or a preventive method, your technicians need more data if they’re going to make any progress.

UE Systems - UP-401 Grease Caddy Pro

The Ultraprobe® 401 Digital Grease Caddy Pro is the perfect blend of data management software and advanced digital technology. With this all-in-one device, your lubrication personnel can create baseline decibel levels, then take readings before and after lubrication to ensure the asset functions properly. In addition to solving these issues at their source, the device allows for quick cost calculations regarding the lubrication program.

The device is compatible with the Mechbase platform of ARPEDON.

For information on the Ultraprobe® 401 Digital Grease Caddy Pro, contact us.

Anouncing Evocon integration

We are proud to announce compatibility with the excelent Evocon OEE software.


Evocon is a visual and user-friendly OEE software that automates the data collection from machines and provides real-time information about production performance.


Using EVOCON with our Maintnode permanently installed system enables you to:

  • Track production downtime.
  • Track minor stops or speed loss in production.
  • Compare machine performance with other sensor inputs.

These are some of the benefits that our clients harness from the integration with EVOCON’s software:

  • Implement Evocon as a hardware-free solution by using equipment already in place.
  • Implement preventive maintenance procedures.
  • Correlate OEE with machine health.
  • Increase the technical availability of machines.

If you are interested on decreasing downtime due to unplanned maintenance activities and increasing your equipment availability and OEE contact us to offer you our help.

Statistical alarms in diagnostic maintenance program


Alarms in a diagnostic maintenance program are critical for the efficiency of the process. They show where the user’s attention should be focused.

This is because most machines in a plant do not show any problems. Eventually if the alarms are set correctly the user will deal with assets that have a real problem.

The simplest alarm method is the comparison of the current value with the base value. However, changes in the operation of the equipment (speed, load) or even environmental conditions changes, can affect the size that the sensors we use measure creating the risk of false alarms. These reduce confidence in the diagnostic maintenance system implemented by enhancing the risk of hiding real damage.

The international maintenance community is increasingly recommending the use of statistic methods for monitoring equipment to combat the phenomenon. The statistical analysis explains how much something can deviate from the ‘normal’ situation. This method is based on the notion of standard deviation or σ. The distribution of data is visually described by the following figure:

Measurements up to 1 x σ from the average, constitute the 68% of the measurements while measurements up to 2 x σ constitute the 95% of the measurements. As can be understood, data even further from the center are certainly indications that the machine’s operating condition is outside ‘normal’.

As part of the continuous improvement of our Mechbase software, we have added an assistant guide for the definition of statistical alarms.

The user having collected data with any of the supported methods, transitions to the measurement point. There they will come across the new option:

Statistical Alarms


Then they will be asked to choose the measurement on which they will be based on. For oscillation measurements this might be RMS, Peak, Peak-to-Peak, Crest factor acceleration/velocity/offset. Regarding spectral analysis statistical alarms are also applied to arrange region value.

statistical alarms choice

Based on the measurements selected, the guide suggests values for the alarms. At this point the used who is acquainted with the machine’s behavior may want to make changed and eventually finalize the alarms.

add statistical alarms


For a diagnostic maintenance program, the time spend on alarms is one of the most cost-effective throughout the program. We ensure that these costs are even lower by optimizing the outcome.

If you are interested in improving the reliability of your equipment click here.

MAINTNODE installation - CMMS integration for HERRCO

Hellenic Recovery Recycling Corporation trusts ARPEDON’s MAINTNODE permanent systems as a part of a complete preventive maintenance program for 9 recycling plants. Permanent condition monitoring sensors where installed (ultrasound and acceleration) for the real time bearing supervision of the main production assets.

Data collection main unit
Data collection main unit
Data collection sub-unit with permanent ultrasonic sensors
Data collection sub-unit with permanent ultrasonic sensors

Moreover, the MAINTNODE system was configured for tracking the operation time of each asset independently. Hence, the ability is given for real time knowledge on the production performance as well as on the equipment structural status, via one system only.

Real time diagram of the shut down and restart operation times of the engine
Real time diagram of the shut down and restart operation times of the engine
Real time sensor diagram
Real time sensor diagram

The data are being collected in MECHBASE, ARPEDON’S online cloud platform. In this platform, the installation data for each asset is presented, with analytical diagrams of the sum of measurements.  Also, alarms were set for each asset separately via the MECHBASE platform.

Finally, there was an integration of ARPEDON’S systems with HERRCO’s maintenance software (CMMS). That way, the maintenance staff workflow will not change as they will be using the tools they are used to (CMMS). It will be more informative though as they will receive additional information about the real condition of the equipment (productivity indicator-KPI’S and strain level of the machine parts).

For more information regarding the products, you can contact us either by phone or via our website’s contact form.

9th Training and Certification for Ultrasounds - Level Ι

Another successful Cat Ι ISO 18436-8 / LEVEL I ASNT SNT-TC-1A training / certification on predictive maintenance with ultrasounds, took place at  GYFADA BEST WESTERN FENIX HOTEL for the 9th time.

The training was organised from 2 to 5 April. The specialised instructor was Craig Armstrong  from UE Systems Inc.

Congratulation to all the participants.

Τhe companies that participated at Cat Ι / Level I were ΟΤΕ – COSMOTE, LOULIS MILLS and ELVALHALCOR.

Stay tuned for the next events that will follow.

Training and Certification for Ultrasounds

Another successful Cat Ι ISO 18436-8 / LEVEL I ASNT SNT-TC-1A training / certification on predictive maintenance with ultrasounds, took place at ARPEDON P.C. for the 8th time.

The training was organised from 24 to 27 April. The specialised instructor was the well-known trainer Peter Boon from UE Systems Inc.

The certification success rate was 100%!

Congratulation to all the participants.

Stay tuned for the next events that will follow.

Equipment maintenance in the IoT era

With the requirements to continually grow, it is important that the production line remains constantly at the optimum level of operation. Using new technologies and equipment maintenance practices, this is now affordable, easy and above all effective.

Analysis of the value of advanced maintenance techniques

Imagine that you installed a new packaging machine on your production line to pack large items, three months ago. For the packaging requirements of your production line, switch between the new machine and the existing  old one. So during these  three months you’ve packed 5,000 items in the new stack. However, the manufacturer proposes to change the bearings every three months or every 15,000 packages. Three months after the purchase of the machine, you have to make a precise (thorough) change of the bearings in order to comply with the manufacturer’s instructions. This is an example of preventive maintenance.

Diagnostic and monitoring system for electromechanical installations using multiple sensors.

Analysis of the value of new maintenance techniques

Now, imagine that the machine you have  installed has been inserted in your maintenance program. With a combination of sensors, you are constantly checking the state of your asset. Having used  the packaging machine for 6 months and having  packed 19,000 items, you receive a notice that you still have 1,000 packages until the next  change of bearings is due. This is an example of predictive maintenance. Prevents damage and alerts you for maintenance work that is adapted to your own use for the equipment in advance before there is a risk of damage.

Preventive Maintenance VS Predictive Maintenance

Industrial sectors are already in accordance  with the concept of preventive maintenance, but predictive maintenance has its own advantages which can enhance  production.

Preventive maintenance work is carried out on the basis of time, events (facts-incidents) or even indications. The age of the equipment as well as the manufacturer’s recommendations are taken into account. In fact, preventive maintenance is a scheduled maintenance. However, as  the example of  the packing machine, this time-based maintenance approach probably it does not represent the actual condition of the equipment and it may  lead to maintenance regardless if this maintenance is necessary according to the condition of the equipment and its components

On the other hand, predictive maintenance is based on actual equipment status instead of time factors. Using a combination of sensors, merging measurements and extracting features is performed. Classification is performed based on algorithmic  predictions  / or experts’ opinion damages can be predicted  before being incurred, so ample time is  given to the company to plan the maintenance. This allows field engineers to fix the damage before it ever occurs.

As is evident in predictive maintenance, advanced techniques and sensors are used, such as:

  • Oscillation sensors (Accelerometers) measure the motion of the camera and detect mechanical errors that are evolving.
  • Current analyzers monitor the status of the electrical components of the system.
  • Temperature sensors.
  • Thermal remote images with mobile devices are used to access and store the temperature and infrared image of the production equipment.
  • Ultrasound sensors are used to detect leaks- inspect mechanical and electrical components.

Extension of Applications

What is the reason for using the preventive meeting since it has such positive results?

However, predictive maintenance offers significant cost savings by reducing downtime and lowering the cost of other parts and spare parts.  Investing in a predictive maintenance system accounts for up to 10 times its cost to the oil and gas industry, according to a Roland Berge study.

One can easily and quickly measure points of interest even with multiple different sensors at the same time. In addition, one can  access the state of the plant from anywhere and make decisions about their maintenance and operation. With the fixed systems and the  Internet of Things (IOT), it is possible   to repeat accurate and complete measurements in inaccessible or remote locations at any time without the need for staff relocation.

When the following are implemented on a software platform that is flexible and safe, the results are unsurpassed to the usual maintenance and tracking practices that  exist to date. It is obvious that predictive maintenance is an attractive worthy  investment that brings excellent  results.